U.S. patent application number 17/380562 was filed with the patent office on 2022-01-20 for apparatus and method for electrofusion welding of reinforced thermosetting resin pipe joints.
This patent application is currently assigned to SAUDI ARABIAN OIL COMPANY. The applicant listed for this patent is SAUDI ARABIAN OIL COMPANY, TWI Ltd.. Invention is credited to Waleed Al Nasser, Abdullah Al Shahrani, Farshad Salamat-Zadeh, Abderrazak Traidia, Thibault Tarik Villette, Chris Worrall.
Application Number | 20220018479 17/380562 |
Document ID | / |
Family ID | 1000005795721 |
Filed Date | 2022-01-20 |
United States Patent
Application |
20220018479 |
Kind Code |
A1 |
Traidia; Abderrazak ; et
al. |
January 20, 2022 |
APPARATUS AND METHOD FOR ELECTROFUSION WELDING OF REINFORCED
THERMOSETTING RESIN PIPE JOINTS
Abstract
A system for coupling pipes includes a first pipe having a
tapered, spigot end; a second pipe having a tapered, spigot end;
and a coupler having two tapered socket ends adapted to internally
receive the respective tapered, spigot ends of the first pipe and
the second pipe. The first pipe and the second pipe are made from a
reinforced thermosetting resin (RTR). The coupler comprising a
resistive element implanted therein and connected to electrodes
extending to an exterior of the coupler. A thermoplastic material
is disposed between an exterior of the first pipe and an interior
of the coupler. A thermoplastic material is disposed between an
exterior of the second pipe and the interior of the coupler. Upon
application of electricity to the electrodes, the resistive
elements are heated sufficiently to melt the thermoplastic material
such that, when the heat is removed, the hardened thermoplastic
material seals the first pipe and the second pipe to the coupler. A
method of coupling pipes includes disposing a thermoplastic
material between an exterior of a first pipe and an interior of a
coupler; disposing a thermoplastic material between an exterior of
a second pipe and the interior of the coupler; inserting the first
pipe and the second pipe into the coupler; and applying of
electricity to electrodes of the coupler such that resistive
elements of the coupler heat sufficiently to melt the thermoplastic
material such that, when the heat is removed, the hardened
thermoplastic material seals the first pipe and the second pipe to
the coupler.
Inventors: |
Traidia; Abderrazak;
(Lussan, FR) ; Al Shahrani; Abdullah; (Dammam,
SA) ; Worrall; Chris; (Cambridge, GB) ;
Salamat-Zadeh; Farshad; (Cambridge, GB) ; Al Nasser;
Waleed; (Ad Dammam, SA) ; Villette; Thibault
Tarik; (Belfort, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAUDI ARABIAN OIL COMPANY
TWI Ltd. |
Dhahran
Cambridge |
|
SA
GB |
|
|
Assignee: |
SAUDI ARABIAN OIL COMPANY
Dhahran
SA
TWI Ltd.
Cambridge
GB
|
Family ID: |
1000005795721 |
Appl. No.: |
17/380562 |
Filed: |
July 20, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
63053915 |
Jul 20, 2020 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29L 2031/24 20130101;
B29C 65/3476 20130101; B29C 65/3468 20130101; B29C 65/3424
20130101; F16L 47/03 20130101 |
International
Class: |
F16L 47/03 20060101
F16L047/03; B29C 65/34 20060101 B29C065/34 |
Claims
1. A system for coupling pipes comprising: a first pipe having a
tapered, spigot end; a second pipe having a tapered, spigot end;
wherein the first pipe and the second pipe are made from a
reinforced thermosetting resin (RTR), a coupler having two tapered
socket ends adapted to internally receive the respective tapered,
spigot ends of the first pipe and the second pipe, the coupler
comprising a resistive element implanted therein and connected to
electrodes extending to an exterior of the coupler, wherein a
thermoplastic material is disposed between an exterior of the first
pipe and an interior of the coupler, wherein a thermoplastic
material is disposed between an exterior of the second pipe and the
interior of the coupler, wherein, upon application of electricity
to the electrodes, the resistive elements are heated sufficiently
to melt the thermoplastic material such that, when the heat is
removed, the hardened thermoplastic material seals the first pipe
and the second pipe to the coupler.
2. The system of claim 1, wherein the coupler is made of the
reinforced thermoplastic material.
3. The system of claim 1, wherein at least one of the first pipe,
the second pipe, and the coupler is coated with a thermoplastic tie
layer.
4. The system of claim 1, wherein all of the first pipe, the second
pipe, and the coupler are coated with a thermoplastic tie
layer.
5. The system of claim 1, wherein the resistive element is a
metallic coil.
6. The system of claim 5, wherein the resistive element is at least
a portion of the metallic coil directly exposed to the interior of
the coupler.
7. A method of coupling a first pipe and a second pipe with a
coupler, wherein the first pipe and the second pipe are made from a
reinforced thermosetting resin (RTR) and each have a tapered,
spigot end, wherein the coupler has two tapered socket ends adapted
to internally receive the respective tapered, spigot ends of the
first pipe and the second pipe, the coupler comprising a resistive
element implanted therein and connected to electrodes extending to
an exterior of the coupler, the method comprising: disposing a
thermoplastic material between an exterior of the first pipe and an
interior of the coupler; disposing a thermoplastic material between
an exterior of the second and an interior of the coupler; inserting
the first pipe and the second pipe into the coupler; and applying
of electricity to the electrodes such that the resistive elements
heat sufficiently to melt the thermoplastic material such that,
when the heat is removed, the hardened thermoplastic material seals
the first pipe and the second pipe to the coupler.
8. The method of claim 7, wherein the coupler is made of the
thermoplastic material.
9. The method of claim 7 further comprising: coating at least one
of the first pipe, the second pipe, and the coupler with a
thermoplastic tie layer.
10. The method of claim 7 further comprising: coating all of the
first pipe, the second pipe, and the coupler with a thermoplastic
tie layer.
11. The method of claim 7, wherein the resistive element of the
coupler is a metallic coil and at least a portion of the metallic
coil is exposed to the interior of the coupler, the method further
comprising connecting the electrodes of the coupler to ground so as
to discharge static electricity built up on the first pipe or the
second pipe.
Description
BACKGROUND OF INVENTION
[0001] RTR (Reinforced Thermosetting Resin) pipe is an acronym
given to a broad family of fiber reinforced thermosetting pipes
manufactured via a filament winding process. The reinforcement is
generally glass fiber and the resin (matrix) is a thermoset
polymer, traditionally polyester, vinyl-ester, or epoxy depending
on the nature of the transported fluids in the pipe and the service
temperature. This has led to the development of 3 main product
lines for RTR pipes; GRP (Glass Reinforced Polyester), GRV (Glass
Reinforced Vinylester) and GRE (Glass Reinforced Epoxy) pipes.
[0002] RTR pipes are generally produced in rigid segments of about
10-12 meters in length and transported onsite before being
eventually assembled (jointed) to each other to the required
length. The historical development of RTR began with the need to
replace heavy concrete and steel pipes used in utilities and
potable/sewage water systems. However, the use of RTR pipes in
higher value applications such as oil and gas (O&G) service
(particularly GRE), has gained a great deal of attention and
acceptance. Currently, thousands of kilometers of RTR pipes are
installed globally (particularly in the Middle East region) on
yearly basis to meet the need of critical applications such as high
pressure water injection and sour crude oil flowlines. The
experience of O&G operators over the last decades has shown
that RTR is a mature technology and can be an economical
alternative to traditional carbon steel pipes, particularly in view
of the fact that RTR pipe is not subject to the same corrosion seen
in carbon steel piping. Depending on the manufacturer's product
portfolio, RTR line pipes are generally available in diameters
ranging from 11/2'' to 44'' and can be designed to handle pressures
ranging from 150 psi to 4000 psi and temperatures up to 210.degree.
F.
[0003] Within the RTR pipe manufacturing industry is well-known
that the joint/connection in an RTR pipeline system is often the
limiting component towards a higher temperature and pressure
operating envelope. The envelope is often defined in terms of the
product pressure in view of the diameter (i.e., larger diameter RTR
pipe generally cannot handle the same pressure as smaller diameter
piping). Indeed, the experience of O&G operators has shown that
most failures/leaks in RTR pipe systems are associated with joint
failures. This could potentially reduce the confidence in the
material and technology.
[0004] A number of proprietary joint designs have been developed
over the years by the manufacturers, which can generally be grouped
into two main types/categories; adhesive/bonded joints and
interference joints. The former, adhesive/bonded joints, relies on
an adhesive (or a laminate in case of wrapped/laminated joints) to
transfer the load from one pipe to another and the
performance/limitation of such joints is often associated with
proper surface preparation, particularly in field conditions. The
latter, interference joints, relies on a solid contact and direct
load transfer between the two RTR pipes to be jointed, such as
threaded and key-lock joints. A combination of both techniques
(i.e, adhesive and interference) is also possible (e.g., the
Injected Mechanical Joint--IMJ).
[0005] In general, high-pressure RTR pipes make use of interference
or mechanical joints (threaded or key-lock joints), while lower
pressure ratings can be achieved with adhesive and laminate joints.
Examples of interference joints are shown in FIG. 1A, which shows
an integral threaded joint, FIG. 1B, which shows a coupled threaded
joint, and FIG. 2, which shows a key-lock joint. Referring to FIG.
1A, the joint 100 is formed between a first RTR pipe 102 having a
threaded spigot end and a second RTR pipe 104 having a threaded
socket end. Referring to FIG. 1B, joint 110 is formed between a
first RTR pipe 112 having a threaded spigot end and a second RTR
pipe 114 also having a threaded spigot end by employing a coupler
pipe 116 having threaded socket ends. Referring to FIG. 2, joint
200 is formed between an RTR pipe 202 having a spigot end and an
RTR pipe 204 having a socket end using locking strips 206 and a
rubber sealing (O-ring) 208.
SUMMARY OF INVENTION
[0006] One or more embodiments of the present invention relate to a
system for coupling pipes comprising: a first pipe having a
tapered, spigot end; a second pipe having a tapered, spigot end;
wherein the first pipe and the second pipe are made from a
reinforced thermosetting resin (RTR), a coupler having two tapered
socket ends adapted to internally receive the respective tapered,
spigot ends of the first pipe and the second pipe, the coupler
comprising a resistive element implanted therein and connected to
electrodes extending to an exterior of the coupler, wherein a
thermoplastic material is disposed between an exterior of the first
pipe and an interior of the coupler, wherein a thermoplastic
material is disposed between an exterior of the second pipe and the
interior of the coupler, wherein, upon application of electricity
to the electrodes, the resistive elements are heated sufficiently
to melt the thermoplastic material such that, when the heat is
removed, the hardened thermoplastic material seals the first pipe
and the second pipe to the coupler.
[0007] One or more embodiments of the present invention relate to a
method of coupling a first pipe and a second pipe with a coupler,
wherein the first pipe and the second pipe are made from a
reinforced thermosetting resin (RTR) and each have a tapered,
spigot end, wherein the coupler has two tapered socket ends adapted
to internally receive the respective tapered, spigot ends of the
first pipe and the second pipe, the coupler comprising a resistive
element implanted therein and connected to electrodes extending to
an exterior of the coupler, the method comprising: disposing a
thermoplastic material between an exterior of the first pipe and an
interior of the coupler; disposing a thermoplastic material between
an exterior of the second and an interior of the coupler; inserting
the first pipe and the second pipe into the coupler; and applying
of electricity to the electrodes such that the resistive elements
heat sufficiently to melt the thermoplastic material such that,
when the heat is removed, the hardened thermoplastic material seals
the first pipe and the second pipe to the coupler.
[0008] Other aspects and advantages of the invention will be
apparent from the following description and the appended
claims.
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIGS. 1A and 1B show an integral and a coupled threaded
joint, respectively.
[0010] FIG. 2 shows a key-lock joint.
[0011] FIG. 3 is a schematic representation of overloading failure
of threaded RTR connections.
[0012] FIG. 4 is a schematic 3D representation of an RTR jointing
system in accordance with an embodiment of the present
invention.
[0013] FIG. 5 is a schematic cross-section representation of an RTR
jointing system in accordance with an embodiment of the present
invention with different position for the resistive implants.
[0014] FIG. 6 is a schematic 3D representation of an RTR jointing
system in accordance with an embodiment of the present
invention.
[0015] FIGS. 7A-7C are schematic cross-section representations of
an RTR jointing system in accordance with an embodiment of the
present invention with different position for the resistive
implants.
[0016] FIG. 8 is a schematic description of a method of assembling
a coupling system in accordance with embodiments of the present
invention.
[0017] FIG. 9 is an illustration of using a system in accordance
with embodiments of the present invention as a means to mitigate
electrostatic discharge (ESD) and dissipate accumulated static
charges.
DETAILED DESCRIPTION
[0018] Threaded joints are traditionally used for high pressure RTR
pipes. These can be either "integral" (i.e., a connection that does
not use a joining member/coupler to transfer the load from one pipe
to the other) or using a "coupler." Although threaded joints can
achieve outstanding performance, in terms pressure rating and
sealing capacity, the experience of O&G operators has shown
that failures can happen. The general opinion is that the failures
are associated with improper installation by the jointers (pipe
misalignment, over-torqueing, improper/insufficient taping of the
thread compound--TEFLON.RTM. (a trademark of the The Chemours
Company FC, LLC), etc.).
[0019] A typical failure mechanism is illustrated in FIG. 3. A poor
installation can result in imperfections/cavities along the contact
surface between the spigot and the socket. In operation, fluid
(e.g., water) at high pressure and high temperature could ingress
into these cavities (step #1) and create a high pressure fluid film
(step #2) which would slowly propagate along the spigot-socket
interface. In some cases, the creep of the resin at the interface
can aggravate the water propagation at the interface. As the
ingress progresses, the contact pressure on the initial threads is
eliminated and the excess load is transferred to the nearby
threads, which eventually leads to overloading failure (step
#3).
[0020] One or more embodiments of the present invention introduce a
new jointing technique that will reduce, and potentially eliminate,
failures and increase the confidence in the RTR pipe technology.
The ultimate target for such embodiments is to replace current
jointing technologies for RTR pipes (low and high pressure) with a
maximum operating envelope up to 24'' at 1500 psi pressure rating
and service temperatures above 200.degree. F.
[0021] Therefore, one or more embodiments of the present invention
relate to a system and method for jointing of high pressure
reinforced thermosetting resin (RTR) pipes using electrofusion
welding process, also referred to as resistive implant welding.
More specifically, one or more embodiments relate to a system and
method for advanced coupling and sealing of high pressure
reinforced thermosetting resin (RTR) pipes. The system comprises:
(1) two "weldable" RTR pipes with tapered spigot ends coated with a
tie layer (interlayer) comprising at least a thermoplastic material
and (2) a "weldable" RTR coupler with tapered socket ends coated
with a tie layer comprising at least a thermoplastic material and
resistive implant elements. In one or more embodiments, the RTR
coupler is replaced by a reinforced thermoplastic electrofusion
coupler that meets the same technical requirements. Additionally, a
method of jointing/coupling the two RTR pipes includes: (1) pushing
the two RTR pipes into the tapered reinforced coupler (to ensure
the tie layers are compressed against each other) followed by (2)
fusion welding of the pipes to the coupler using resistive welding
(electrofusion).
[0022] An exemplary system in accordance with one or more
embodiments is schematically presented in FIG. 4 and FIG. 5. As can
be seen, a joint 400 is being formed between a first RTR pipe 402
with a tapered spigot portion (end) coated with a tie layer
comprising at least a thermoplastic material (tie layer A) 408 and
a second RTR pipe with a tapered spigot portion (end) coated with a
tie layer comprising at least a thermoplastic material (tie layer
A) 408 by employing a reinforced thermoset (RTR) coupler pipe 406
with a tapered socket portions (ends) coated with a tie layer
comprising at least a thermoplastic material (tie layer B) 408 and
incorporating resistive implant elements (such as metallic coils,
sheet, meshes, etc.) 410. The resistive implant elements 410 are
connected to electrodes 412, which extend from the coupler pipe
406.
[0023] The main role of the tie layers (A and B) is to make the
thermoset parts "weldable" and, therefore, enable the permanent
interlock of the spigots to the coupler. On top of that, the
thermoplastic interlayers (or tie layers) will provide the required
sealing to the joint upon completion and will eliminate the need
for a secondary sealing system, such as O-rings. The axial length
of the bonding line (i.e., the length of the coupler) must be large
enough to provide the required joint strength (a larger coupler
length gives a larger surface area to transfer the load and
increases the overall strength, as defined by the load bearing
capacity of the joint).
[0024] Those skilled in the art will appreciate various methods can
be used to apply and bond the tie layers to the thermoset parts.
Several techniques, such as thermal spraying a thermoplastic powder
on the faying surface of the thermoset (with sufficient surface
preparation, e.g., sand blasting) or applying a thermoplastic
implant while the thermoset is in a partially cured (or uncured)
state, followed by co-curing at the required temperature (below the
melting temperature of the thermoplastic) may be employed in
different embodiments. In one or more embodiments, the deposition
of tie layers may be conducted in the factory at the manufacturing
stage. Because the surface preparation of a substrate often
conditions the final quality of a coating, a clean and controlled
environment (e.g., dust free, temperature regulation, etc.) is
advantageous, which is easier to achieve in the manufacturing
site.
[0025] The thermoplastic materials 408 used on the tie layers can
either be the same or different in A and B, but must necessarily be
weldable to each other (e.g., have very close
melting/solidification temperatures and be melt compatible, i.e.,
mix well when molten). In addition, such thermoplastic materials
must be carefully selected to ensure their function throughout the
lifetime of the pipe (typically, 25 years). For example, the
materials must be qualified (e.g., as per ISO 23936) to meet the
service specifications in terms of design temperature, pressure and
chemical compatibility with the environment (acidic gases, liquids,
aromatics contents, etc.). Examples of thermoplastics that can be
considered, include but are not limited to (i.e., non-exhaustive
list), are HDPE, PE-RT, PVDF, PEEK, PEKK, PA12, POK among other
thermoplastic resins commonly used in the O&G industry.
[0026] As schematically illustrated in FIG. 5, the resistive
implant elements 410 can either be (i) incorporated within the
thermoset RTR coupler 406 adjacent to the thermoplastic tie layer
(tie layer B) 408 or (ii) within the thermoplastic tie layer (tie
layer B) 408 itself near the fusion line/surface. The selection of
one variant over the other will depend (among others) on the
coupler manufacturing process and the characteristics of the
thermoplastic polymer used for the thermoplastic tie layers 408. In
the first case (i), the resistive implements can be incorporated
during the filament winding process when manufacturing the RTR
coupler 406, which is particularly adapted for the case where
metallic wires are used as implants. The second case (ii) is
particularly adapted when using a thermoplastic polymer tie layer
with high melting temperature (such as PEEK). Indeed, in such case,
the large amount of heat required to melt the tie layer material
could result in degradation of the RTR resin and reinforcements in
the coupler. Therefore, the heat generation source (i.e, the
resistive implants 410) must be localized near the fusion line
(near the free surface of the tie layer).
[0027] In one or more embodiments, a variant to the system
described earlier is illustrated in FIG. 6. A joint 600 is formed
between RTR pipe 602, RTR pipe 604, and coupler pipe 606, in which
the coupler pipe 606 is made of a reinforced thermoplastic material
incorporating resistive implant elements 410. Such a configuration
eliminates the need for a thermoplastic tie layer (tie layer B) 608
inside the coupler 606. In one aspect, this configuration could be
easier to adopt because reinforced thermoplastic electrofusion
couplers are readily available (although, in another aspect, an RTR
coupler is likely to be a more cost effective, but at the expense
of an additional step to make the coupler "weldable"). The
particular coupler material used can be selected according to two
main criteria: (1) proper weldability to the thermoplastic material
used in tie layer A, and (2) meeting the minimum required long term
performance of the joint (strength, stiffness, chemical resistance,
and permeation barrier).
[0028] Those skilled in the art will appreciate that the exemplary
embodiments disclosed are merely schematic illustrations and that
many other variations may be made in design or geometry (e.g., use
of metallic sheet or mesh instead of coiled wires, thermally
sprayed metallic sheet, etc.) without departing from the scope of
the present invention. In particular, although the figures show
that the thermoplastic tie layer inside the RTR coupler is broken
into two individual tie layers (one on each taper end), a single
tie layer extending from one end to the other may be used in one or
more embodiments. Such a configuration would be practical to
manufacture and may provide additional fluid permeation barrier to
the RTR coupler.
[0029] As schematically illustrated in FIGS. 7A-7C, in another
potential variation, a single "thick" thermoplastic inter-layer 708
may be used on one face of the joint 700 only (i.e, either the RTR
pipe 702, 704 side or on the coupler 706 side), leaving the other
side uncoated. Provided that sufficient surface preparation is
performed on the uncoated RTR pipe 702, 704 joining (e.g.,
abrasion), the joining process described below will lead the
thermoplastic interlayer to fuse and bond (physically and/or
chemically) to the uncoated RTR part. Although this variant
eliminates the requirement for coating both sides of the RTR joint
700, which can be challenging in some circumstances, embodiments
employing such a variation may negatively affect performance in
terms of bonding strength.
[0030] A method of assembling any of the systems described above is
illustrated in FIG. 8. As those of skill in the art will
appreciate, the same procedure can be followed for any of the
system variants presented. The assembly method involves a
conventional electrofusion welding process, which will not be
described in detail herein.
[0031] Referring to FIG. 8, upon taking sufficient precautions at
the installation site to make sure that the two RTR pipes are
properly aligned (Step 1), the pipes are pushed into the reinforced
coupler to bring the thermoplastic layers into contact with each
other (Step 2). The pipe and coupler ends must have enough geometry
(here "tapered" as an example) to allow sufficient contact
(compression) between the thermoplastic interlayers and the coupler
and maintain contact throughout the joining process. The last step
(step 3) is the electrofusion of the coupler to the RTR pipes (an
electric current is passed through the resistive implants to
generate enough heat to melt part of the thermoplastic layers on
the pipes and the coupler, and upon solidification, a joint is
formed). Note that in step 3, AC current is shown for illustration
purposes only and DC current could also be used during the
electrofusion process.
[0032] Following a controlled cooling (the degree of crystallinity
in the thermoplastic layer may be dependent on the rate of cooling)
and full solidification, the RTR pipes are joined and also sealed.
The thermoplastic interlayer will act as a (1) load transfer from
one pipe to the other, and also, (2) as a barrier to prevent any
permeation and/or leak of the transported fluids. This eliminates
the need for secondary sealing mechanism, such as O-rings.
[0033] It is worth noting that the tie layer will mainly be subject
to axial load/stresses during pipe operation (hoop stresses are
mainly carried by the RTR pipes and the reinforced coupler).
Therefore, the length of the reinforced coupler (i.e., the total
contact surface between the coupler and the pipes) must properly
designed (i.e., large enough) to ensure the shear load on the
thermoplastic interlayers does not exceed their capacity. The
latter being mainly dependent on the shear strength of the
thermoplastic material used and to the bonding strength between the
tie layers and the RTR parts.
[0034] One or more embodiments of the present invention as
described above may solve one or more of the following problems or
provide one or more of the following advantages.
[0035] Advantageously, there is an important "by-product" of the
systems disclosed herein, which is related to the prevention of
electrostatic discharge (ESD) in composite pipes. ESD is a
well-known problem in plastic pipes (and non-conductive pipes in
general) used in gas transportation and is related to the
accumulation of static charge/electricity along the pipe length due
to the electric interaction between suspended solid particles
(e.g., sand) or water droplets in the gas stream. Such static
electricity, which normally is dissipated to the ground in
conventional metallic pipes (conductors) cannot be dissipated in
plastic/composite pipes. Accordingly, the static electricity
accumulates along the length of the pipe and then can discharge at
downstream metallic components (valves or tanks), possibly creating
a failure. One solution to this problem lies in making the pipes,
or a portion of the pipeline, electrically conductive in order to
dissipate the static charges.
[0036] A by-product of the systems described herein involves using
the RTR joints, which are distributed on a regular distance along
the pipe length, as a means to locally discharge the accumulated
static electricity. Indeed, as illustrated in FIG. 9, the idea
consists of exposing some of the resistive implants to the free
surface (i.e., allowing contact with the transported fluids) at the
inner surface of the pipe and connecting the electrofusion terminal
to the ground post installation. By doing so, a conductive/electric
path to the electric charges to flow from the inner surface of the
pipe to the external ground is provided.
[0037] Additionally, systems described herein are advantageous
because it is known that the integrity of conventional RTR joints
(threaded or adhesive joints) is highly dependent on the skills of
the jointer during installation. For example, a joint misalignment,
improper application of TEFLON.RTM. compound on the threads or
excessive torqueing during the joint installation will inevitably
impact the interference (contact) pressure between the spigot and
socket threads. Further, the degradation of the sealing systems
(secondary O-rings) used in some of the joints (e.g., key lock) are
known to be the main source of leaks. Thus, the alternative way of
joining RTR pipes through a welding process as is described herein
simplifies the process and avoids such problems. Also,
electrofusion welding is a most efficient and effective joining
solution for standalone thermoplastic pipes (mainly polyethylene),
reinforced thermoplastics, and the like.
[0038] One or more embodiments may provide improved sealing and
reliability over prior systems. The sealing is entirely provided by
the thermoplastic tie layers after welding. In conventional joints,
the sealing is provided by a contact pressure (O-ring for key
lock-joints or TEFLON.RTM. wrap in threaded joints). The contact
pressure degrades over time and joints end up leaking. In
embodiments of the present invention, the sealing is permanent
(welded). In addition, the effective joining area is larger and
thus the permeation path is longer, resulting in a lower long term
leak of harmful substances to the environment.
[0039] One or more embodiments may provide increased joint strength
provided by a larger joining area (i.e., the length of the coupler)
and controlled mainly by the strong bonding between the
thermoplastic interlayer to thermoset parts.
[0040] One or more embodiments may allow for de-skilled
installation, as compared to conventional joints, where the quality
of the joints often depends on the skills of the jointer (surface
treatment, injection of resin, proper application of TEFLON.RTM.
sealing compound on-site, installation of O-ring, torqueing, etc.).
In embodiments of the present invention, the application of the tie
layers at the pipe ends can be done at the manufacturing site
(controlled production) and the skills required by the jointer at
the installation site are reduced. Also, the electrofusion welding
process can be automated.
[0041] One or more embodiments provide versatility. With the
potential to easily change the joint design and performance, even
on-site, through modification of the pipe end taper geometry.
Embodiments of the present invention make the joint easily
repairable on-site (thermoplastic welding is a reversible process
unlike thermoset curing). In addition, embodiments of the present
invention can be possibly used as a repair technique on straight
sections of RTR pipes. The latter must be modified on-site to
incorporate the connecting coupler and the thermoplastic
interlayers.
[0042] One or more embodiments provide ESD risk mitigation.
Embodiments of the systems described herein can be used to
dissipate static charges and mitigate the risk for ESD.
[0043] While the invention has been described with respect to a
limited number of embodiments, those skilled in the art, having
benefit of this disclosure, will appreciate that other embodiments
can be devised which do not depart from the scope of the invention
as disclosed herein. Accordingly, the scope of the invention should
be limited only by the attached claims.
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